_Remarks._--In life the dorsum in males is dull olive-green; the groin, anterior and posterior surfaces of the thighs, inner surfaces of limbs, and upper arms are dark brown. The ventral surfaces of the limbs are pinkish tan; the other ventral surfaces are pale creamy tan with reddish brown spots. The suborbital spot is pale greenish tan, and the iris is deep reddish brown. In females the dorsum is dull olive-brown; the anterior part of the head is tan, and the suborbital spot is yellowish tan. The groin and hidden surfaces of the limbs are dark reddish brown. The ventral surfaces of the limbs are brown; the throat and chest are creamy white, and the belly is reddish tan, both with dark brown mottling. Considerable ontogenetic change occurs in coloration. Juveniles are pale above with a dark median dorsal blotch and dark transverse bars on the limbs. The venter is white. The change consists principally of an increase in dark pigment and subsequent obliteration of the juvenile pattern. Tadpoles of this species have moderately long tails with low fins, robust bodies, two rows of labial papillae with median part of the upper lip bare, and two upper and five lower rows of teeth. Trueb and Duellman (1970) described the eggs, tadpoles, mating call, and variation in the adults. GENERIC RELATIONSHIPS Among the 33 genera currently recognized in the family Hylidae, there are two basic types of vocal sac structure (Duellman, 1970b), namely the subgular type and the lateral type. Only four hylid genera, all Neotropical lowland groups, are known to possess paired lateral vocal sacs; these are _Osteocephalus_, _Argenteohyla_, _Phrynohyas_, and _Trachycephalus_. The geographical distributions and morphological characteristics of these four genera suggest that they are more closely related to one another than with any other hylid genera. Of the four genera, _Osteocephalus_ is the most generalized in morphology, and, like _Phrynohyas_, has no specialized habits. _Osteocephalus_ and _Argenteohyla_ are similarly distinguished from _Phrynohyas_ and _Trachycephalus_ on the basis of vocal sac structure. The vocal sacs of _Osteocephalus_ and _Argenteohyla_ are posterior and protrude posterolateral to the angles of the jaws when they are inflated, whereas those of _Phrynohyas_ and _Trachycephalus_ are more lateral and protrude posterior to the angles of the jaws when inflated.